1. Field of the Invention
The present invention relates to an automatic manuscript sheet feeder to be used in an overhead projector (hereinafter referred to as OHP), and more particularly relates to an automatic sheet feeder with an improved mechanism for feeding and discharging manuscript sheets.
2. Description of the Prior Art
A prior art of the present invention is an automatic manuscript sheet feeder disclosed in the Japanese Patent Application Laid-open No. 255474/1990.
A conventional manuscript sheet feeder according to the above invention comprises a feeding means having at least a pair of carrying belts for each of the vertical and horizontal manuscript sheets located around the stage glass, a detection means to detect the manuscript direction (vertical or horizontal) and a manuscript feeding amount control means.
A horizontal manuscript placed on the stage glass is carried forward or backward with a pair of carrying belts arranged on both sides of the stage glass (Left and right of the manuscript feeding direction).
In this prior art, if the rotation speeds of the carrying belts are not correctly the same, the left and right edge of the manuscript are carried at different speeds. This causes distortion and float in a part of the manuscript, which may result in unclear OHP image.
On the other hand, the user may sometimes want to manually set the manuscript on the stage glass without using the automatic mechanism. In such case, the carrying belts on the both sides of the stage glass in the above conventional feeder interfere with manual manuscript setting.
The carrying belts are in contact with a large area of the manuscript on the stage glass to take advantage of the frictional force on the contact face for manuscript carrying. This contact tends to damage the manuscript. In addition, a pair of carry belts and their driving mechanisms require many components.
Another prior art is an OHP device with automatic manuscript replacement function disclosed in the Japanese Patent Application Laid-open No. 259633/1990.
A conventional OHP device according to the above prior art comprises a manuscript feeding control means which feeds the manuscript one by one from the manuscript storage section, a collection control means which controls collecting of manuscripts on the reflective plate of the OHP device and bringing of the same to the collection tray and a remote control means which remotely controls the above manuscript feeding control means and the collection control means.
According to this prior art, it is necessary that a holding roller constituting the above manuscript feeding control means and collection control means is always in pressurized contact with the leading or trailing edge of the manuscript. This means that the size and positioning of the manuscript to be fed are limited.
Still another prior art is a sheet plate making device disclosed in U.S. Pat. No. 5,280,903.
This sheet plate making device comprises a tilt table having an upstream end at a higher position and a downstream end at a lower position on its surface, a plurality of discs having surfaces continuous to the table surface, a plurality of rotatable balls opposite to these discs and an edge guide to regulate the sheet direction straightly. By feeding sheets from the above upstream end onto the table and applying rotational force to the back of the sheet with the above discs, the sheet direction is corrected so that the sheet edge goes along the edge guide.
This prior art device is designed to carry sheets between two devices (printer and another device, for example). It is not particularly provided as a manuscript sheet feeder for OHP. In addition, unique ideas such as a tilt table and a rotational discs incorporated in the table according to this prior art cannot be applied as they are to a manuscript sheet feeder for OHP.
Thus, it is an object of the present invention to provide an automatic manuscript sheet feeder with a new structure which prevents distortion, float and damage of the fed manuscript.
It is another object of the present invention to provide an automatic manuscript feeder which facilitates manual setting of manuscript sheets.
It is still another object of the present invention to provide an automatic manuscript sheet feeder which ensures feeding of a horizontal manuscript, whose edge along the feeding direction is shorter than the edge across such direction (width).